A display device in general includes a display panel configured to display images. The display panel typically includes luminous elements configured to emit light in response to image signals input to the display device. The luminous elements generate heat in synchronization with light emission to represent images. The heat from the luminous elements is likely to be confined inside the display panel. If there is a temperature rise inside the display panel, normal operations of the display panel are often interrupted.
The display device may be exemplified by an organic EL (electroluminescence) display. The organic EL display includes organic EL elements. A luminous layer of an organic EL element is likely to be susceptible to heat. Therefore, a life of a display panel is shortened under an excessive temperature rise inside the display panel.
In order to facilitate heat dissipation from a display panel, it has been considered to install a radiator on the rear surface of the display panel. If a radiator installed on the display panel appropriately radiates heat from the display panel to the outside, an excessive temperature rise is less likely to happen to the display panel.
However, there is not appropriate transfer of heat generated by light emission to the radiator actually because of a low contact level between the display panel and the radiator. Consequently, heat is accumulated inside the display panel to cause a temperature rise of the display panel. Therefore, the luminous layer is likely to deteriorate.
Patent Document 1 discloses a radiation sheet, which is a lamination of an expanded graphite sheet and a net formed of metal wires. The expanded graphite sheet and the net are integrated under a rolling process. If such a radiation sheet is attached to a substrate on which semiconductors of electronic equipment are mounted, heat generated by the semiconductors on the substrate may be transferred to a heat sink through the radiation sheet.
Even if the radiation sheet of Patent Document 1 is used for heat dissipation of a display panel, there may be insufficient heat dissipation effect. Thermal conductivity in the in-plane direction of the radiation sheet as an integrated lamination of the expanded graphite sheet and the net by a rolling process is constant, independent from a position of the radiation sheet. Therefore, unless heat generated at an edge of the display panel is radiated during heat generation in the center area of the display panel, little heat dissipates in the center area of the display panel. Consequently, the heat is confined to the center area of the display panel to cause a local temperature rise. Therefore, even if a conventional radiation sheet is used for a display panel, there is a temperature rise in the center area of the display panel to facilitate deterioration of organic EL elements situated in the center area of the display panel. This results in a drop in brightness in the center area of the display panel. A user watching (observing) a video displayed on the display panel is more likely to pay attention on images in the center area rather than images near the periphery of the display panel. Consequently, a drop in brightness in the center area of the display panel dramatically degrades quality of the video displayed by the display panel.
Patent Document 1: JP 2005-229100 A